Method of making fin tubing



Dec. 8, 1953 E. BRUEGGER 2,551,526

METHOD OF MAKING FIN TUBING Filed Jan. 26, 1944 4 Sheets-Sheet l INVENTOR ERA/57 89056651? BY, and 777mm? ydaaw HIS ATTORNEYS METHOD OF MAKING FIN TUBING Filed Jan. 26, 1944 4 Sheets-Sheet 2 INVENTOR ERA E57 B/PUEGGER 2 44%; 4 gaam/ HIS ATTORNEYS Dec. 8, 1953 E. BRUEGGER 2,661,526

METHOD OF MAKING FIN TUBING Filed Jan. 26, 1944 4 Sheets-Sheet 3 INVENTOR ERNEST EFL/6651? 'H l5 ATTORNEYS Dec. 8, 1953 'BRUEGGER 2,661,526

METHOD OF MAKING FIN TUBING Filed Jan. 26; i944 4 Sheets-Sheet 4 INVENTOR ERA/67 5/?04-6 65/? rus ATTORNEYS ?atented Dec. 8, 1953 l STTES ATENT QFFIQE Ernest Brues er. Massillon, Ohio, assignor to The Grisccm Russell Company, New York, N. Y., a

corporation of Delaware Application January 26, 1944;, Serial No. 519,788

3 .Claims. 1

This invention relates to the manufacture of articles having heat-radiating fins projecting from the surface thereof and especially to the manufacture of finned tubing used extensively in heat exchange apparatus.

One of the objects of the invention is to provide an improved method of grooving the surfaces of articles of malleable material for any desired purpose, and particularly for grooving malleable metal tubes as one of the steps in attaching heat exchanging fins thereto.

Another object of the invention is to provide an improved method of applying strips edgewise to the surface of a malleable article, and more especially to an improved method for applying heat conducting fin strips to metal articles such as tubes or pipes, in which case the fin strips can be applied either lengthwise of the tube or surrounding the tube.

The invention will be understood from a corn sideration of the accompanying drawings and the following detailed description of the invention and of these drawings, it being understood that the drawings illustrate one embodiment of the improved apparatus and that the invention is not limited to the particular apparatus disclosed.

In these drawings:

Fig. l is a view in horizontal section of the improved grooving apparatus arranged to form a helical groove in the surface of a malleable tube, 1;;

Fig. 5 is a view in elevation drawn to a smaller scale showing the grooving apparatus in position on the cross slide of a lathe carriage Fig. 6 is an enlarged fragmentary view partly in section showing the tooth formation of the grooving roll and the arrangement of the driving roll;

Fig. '7 is a fragmentary sectional view drawn to a still further enlarged scale and taken radially through one of the teeth of the grooving roll;

Fig. 8 is a view similar to Fig. 6 showing a modified form of grooving roll;

Fig. 9 shows a longitudinal section of a short length of tubing having helical grooves formed in a portion of its surface in accordance with the improved method of the invention;

Fig. 10 shows in section the grooved portion of the tube of Fig. 9 with a helical fin strip wound edgewise into the helical groove; and

Fig. 11 shows the tubing in its finished form.

Referring first to Figs. 9, 10 and 11 of the accompanying drawings, the improved method of forming a groove in an article of malleable material such as a metal tube I involves furrowing the surface of the article by a plowing action so as to displace the metal of the article in two directions; that is, the metal below the surface of the article is displaced both laterally and outwardly. This forms a groove 2 with the laterally and outwardly displaced material turned over, as indicated at 3, to form ridges (see also Fig. 1) along the sides of the groove, this material remaining attached or integral with the material of the tube body. As shown in Figs. 1 and 9, the furrow is carried around the periphery of the tube in the form of a helix, with successive turns of the furrow spaced apart a suitable distance to accommodate an edgewise wound ribbon or strip of metal to provide the tube with helical fins as indicated at 4 in Figs. 10 and 11.

Fig. 10 shows the fin strip wound edgewise in the helical grooves 2, this being the second step in the improved method of making finned tubing. The third and final step in making the tubing is shown in Fig. 11 wherein the raised ridges 3 of material turned up along the edges of the furrow 2 have been swaged against the opposite surfaces of the bases of the fins 4. This operation may be carried out by pressing, rolling or other suitable swaging action, and is preferably carried out in such a way as to compress the turned up material 3 and force a portion thereof somewhat into the sides of the bases or roots of the fins 4, as indicated at 5, thereby bringing the metal of the fins into intimate and heattransferring relation with the metal of the tube 5.

It will be understood that the grooves and fins may, if desired, be applied lengthwise of the tube, or as a series of circular rings, instead of in helical form.

The preferred form of grooving tool for forming the furrows 2 in the tube is illustrated in Figs. 6 and 7. This tool comprises a disk t of hardened steel which may be secured to operating shaft '5' in any suitable manner such as is illustrated, for example, in Fig. 1, wherein shaft 1 is shown as having at its inner end an integral flange 3 against the side of which grooving tool ii is held by means of a series of rivets 9.

The operating shaft 'i of the grooving tool is rotati'vely supported in a tool support or fixture,

indicated generally by numeral [0, which is arranged on the cross slide l l of the tool carriage I2 of a lathe. The tube l to be grooved is mounted in a chuck I3 on the live spindle of the lathe, a supporting guide It being provided for the outer portion of the tube. A stop l5 may, if desired, be mounted in the tail stock 16 of the lathe to asssist chuck H2 in preventing longitudinal shifting of the tube.

The face of grooving tool 6 is brought into the desired engagement with tube I, to be described below, by manipulating the hand wheel i! (Fig. 5) of the cross slide feed screw of the lathe. A pair of knurled backing rolls i8 (Figs. 2 and 1) is provided on the opposite side of tube i from grooving roll 5 to support the tube under the pressure of the grooving roll. These rolls 16 turn on shafts 19 which are supported by means (not shown) on the carriage 12.

Referring now to Figs. 6 and '7, grooving roll 6 is a disk having a thickness substantially greater than the width of the groove which it is desired to form, and the periphery of the disk is cut away in such a manner as to form beveled marginal portions 25.3 and 21 on opposite sides,

leaving a face 22 which is somewhat narrower than the groove to be formed. The beveled sides 28 and 2| are now scalloped or fluted, as indicated at 23 and 2 4, the fluting 23 being staggered with relation to fluting 24 and thereby providing a series of staggered cutting teeth 25 and 25 on opposite sides of the tool face 22.

In operating the tool it is rotated at a different peripheral speed from that of the surface of the tube, preferably at a slower circumferential speed than the tube, and by turning up on the hand Wheel I l, the face 22 of the grooving tool is forced into the metal of the tube and below the surface thereof. The lathe carriage is fed forward by means of the lead screw 21 of the lathe in timed relation to the rotation of the tube so that the tool will trace a helical path on the tube, as indicated in Fig. 1.

The face 22 of the tool being forced below the surface of the tube, and the tool face being moved relative to the surface of the tube, the teeth 25 and 26 cause the plowing action previously referred to to take place, the metal which has been displaced outwardly also being forced or displaced laterally by the bottoms 28 of the scallops or flutings 23 and 2e and also by the sloping or beveled edges 28 and 2| of the tool.

This outwardly and laterally displaced metal 3 arranges itself in ridges extending along both sides of the furrow 2. The plowing action of the grooving tool causes the metal to be torn away at the corners of the furrow making it somewhat wider than the face 22 of the tool so that the walls of the furrow are parallel, or substantially so, rather than conforming to the tapered sides 28 and 2| of the tool.

The too] just described is employed where the grooves are to be comparatively wide for the reception of a reasonably thick fin strip, the tube I being of the order of 1 inches in diameter and the strip-forming fins 4 being about inch wide and 1 6- ineh thick. When thinner fin strip is to be used, a plain grooving roll 611 such as that illustrated in Fig. 8, may be employed. This roll is similar to grooving roll 5 above described, ex cept for the fact that the scallops or flutings 25 and 26 are omitted and the tool has a narrow non-undulating face 22a of a suitable width to provide the width of groove desired.

Like tool 6, the modified form of tool 60. is also operated at a different, and preferably slower, peripheral speed from that of the tube in which the groove is to be formed. The face 22a is forced into the surface of tube la and this action, together with the slow relative motion between the tool and the tube, causes the formation of a furrow, or groove, by means of a plowing action similar to that described above in connection with grooving tool 6, the metal being worked outward above the surface of the tube rather than being either removed or pressed or rubbed down below the tube surface.

The metal is displaced outwardly and then laterally so as to form raised ridges 3a of material turned up from the interior of the tube and laid over against the outer surface of the tube along the opposite edges of the groove or furrow. Such metal is not removed or cut away from the tube as a chip, but is merely displaced from its original position below the surface of the tube outwardly and then laterally after the manner of the operation of a plow.

Referring to Figs. 1-3, inclusive, the mounting of grooving tool 6 and the mechanism for driving the same at a different and preferably slower peripheral speed than the surface of tube I will now be described.

Tool fixture It comprises a main frame member 23 which is provided at its bottom with a dove tail groove 3i! to fit the cross slide H on the tool carriage l2 and has a vertical face 31 against which a swivel plate 32 is clamped by means of a pair of cap screws 33. These screws are received Within arcuate slots 34 to permit swivel plate 32 to be turned with respect to frame 29, as shown in Fig. 4, so as to position the grooving roll 6 at the correct helix angle. Swivel plate 32 carries a grooving roll support 35 and a driving roll support 36 which are keyed and bolted to it as indicated respectively by key 3? and bolts 38.

Shaft l for grooving roll 5 turns in a bushing 39 fixed in support 35 and also in a bushing it carried in a cover member 4! which is bolted at 62 to support 35. Between bushings 3.9 and ii? a driving gear 43 is keyed to grooving roll shaft 1.

A driving roll 4 having a knurled face 35 for frictionally engaging the surface of tube I to be rotated thereby is arranged substantially in axial alinernent with grooving roll 5 and positioned with its inner face close to the inner face of the grooving roll. These faces are, however, spaced apart from one another by a suitable operating clearance. In order to maintain and adjust this clearance, lock screws 35a shown in dotted lines in Fig. 4 are arranged to pass through apertures in the outer edge portion of support 35 and have their ends threaded into lock bushings 35a. These look bushings are threaded in corresponding apertures in support 38 and their inner ends engage the inner face of support 3'5. Thus by suitably adjusting lock bushings 36a, the inner portions of supports 35 and 36 can be spaced apart from one another to provide the desired clearance between grooving roll 6 and drivin roll 44. Lock screws 35a hold the two supports in the adjusted position.

Driving roll 44 is secured on the inner or right hand end of a shaft 46 which is in approximate alinement with grooving roll shaft '8. The construction by which these two parts are secured to one another may be the same as that described previously in connection with grooving roll 6 and its supporting shaft 7.

Driving roll shaft 46 is supported for rotation in a bushing 41 which is carried by a laterally adjustable supporting member 48. The outer end of shaft 45 turns in a bushing 49 which is mounted in a cover member 56 attached to support 35 by means of bolts 5!. The teeth of a pinion 5:2 on shaft 46 engage the teeth of a gear 55 which rotates on a floating center within a cavity 54 formed in cover member 50. Gear 53 meshes with another gear 55 which is keyed to a shaft 53 which is mounted for rotation in bushings carried by supports 36 and 35, respectively. On the opposite end of shaft 56 is a gear 51 and this gear meshes with a pair of floating center gears 58 symmetrically disposed below and above the axes of shafts l and 56. Gears 58 together actuate driving gear 43 on grooving roll shaft 1. Thus the grooving roll 5 is positively driven by the driving roll 44 through the gearing just described. The over-all gear ratio of the gear train is such that the peripheral speed of the grooving roll 6 is somewhat slower than the surface speed of tube I, the face of the grooving roll and the surface of the tube moving in the same direction.

It is important to be able to adjust slightly the driving roll 45 toward or away from the surface of tube I so as to bring these parts into proper driving engagement while at the same time maintaining the desired adjustment of grooving roll *6 with respect to tube 1 to produce the appropriate depth of groove. To accomplish this relative lateral adjustment between driving roll 45 and grooving roll 6, the main bearing bushing 41 for driving roll shaft 46 is carried in the adjustable supporting member 48 previously referred to. Support 48 is slidable in support 36, being provided at top and bottom with guide ways 59.

An adjusting screw 60 which is threaded into the upper part of support 36 has a beveled lower end which engages the upper rear corner of slidable support 48 and by turning this screw inwardly support 48 can be moved outwardly, thereby adjusting driving roll 45 relative to rooving roll 46. When the adjustment has been completed, set screws 6| are turned into engagement &

with the upper surface of sliding support 48 to hold it firmly in adjusted position. In making this adjustment it is necessary first to loosen nuts 5| by which cover 50 is attached to supporting housing 36 so as to permit the outer end of driving roll shaft 46 to move.

The extent of such relative adjustment between driving roll 45 and grooving roll 6 is comparatively small and the shifting of the engagement of the teeth of driving pinion 52 with floating gear 53' and also the teeth of the latter gear with those of gear 55 does not affect their proper operation. The arrangement of gear 53 on a floating center provides for equal division of the adjustment between the two sets of intermeshing gear teeth. In this connection shaft 56 which supports gear 55 turns in appropriate bearing bushings mounted in the two supporting housings 35 and 36 as may be seen in Fig. 1. S116.- able support 48 is provided with a slotted opening for the passage of shaft 56.

By means of the present invention there has been provided an improved method of grooving articles, particularly heat exchanger tubes, which is useful for grooving tubes or pipes of large diameter, for example, 1 inches, or larger, as well as tubes or pipes of smaller diameter. There has also been provided an improved method of making finned articles such as finned tubes or pipes. The forming of the groove by a furrowing or plowing action does not remove the metal of the tube but merely displaces it in such a way as to facilitate the attaching or winding of the fin strip to or about the article and leaving this displaced material attached to the article and in a shape or form which enables it to be readily swaged into intimate contact with the root or base of the fin strip.

Moreover, the improved apparatus or tool of the invention for carrying out the grooving operation by means of a plowing action is of simple construction, easy to manufacture, and can be used in an ordinary lathe. It wiil be understood that the disclosure of this apparatus is in the nature of an example as to how the apparatus part of the invention may be carried out. Consequently changes may be made in the mechanism disclosed without departing from the spirit or scope of the invention, the scope of which is set forth in the appended claims.

I claim:

1. The method of making fin tubing which comprises furrowing the surface of the tube by a plowing action to displace the material of the tube outwardly without detaching it therefrom, applying a fin strip to the tube with one edge thereof within said furrow, and swaging the displaced material against the surface of said strip.

2. The method of making fin tubing which comprises subjecting the surface of the tube to a plowing action to form a furrow therein having material turned up from below the surface extending lengthwise of the furrow, applying a fin strip to the tube with one edge thereof within said furrow, and swaging the turned up material against the surface of said strip.

3. The method of making fin tubing which comprises furrowing the surface of the tube by a plowing action turning up material from below the surface and leaving it attached to the tube along the edges of the furrow, applying a fin strip to the tube with one edge thereof inserted within said furrow, and swaging said turned up material along the edges of the furrow against the opposite sides of said strip.

ERNEST BRUEGGER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 634,469 Majert Oct. 10, 1899 647,249 Chamberlain Apr. 10, 1900 1,668,534 Berg May 1, 1928 1,858,733 Flachbart May 17, 1932 1,865,575 Locke July 5, 1932 1,928,639 Berg Oct. 3, 1933 2,004,387 Dewald June 11, 1935 2,036,417 Laird Apr. 7, 1936 2,268,983 Gilmore et al. Jan. 6, 1942 2,285,583 Jennings et a1 June 9, 1942 FOREIGN PATENTS Number Country Date 403,734 Great Britain Jan. 4, 1934 

